Several components of cycles have become standardized, and these standards have extended from traditional bicycles to stationary exercise bicycles. Drive trains in particular are very standards oriented. One standard commonly used in both exercise cycles and traditional cycles is the connection of pedals to the crank. Pedals are almost universally connected to the crank using a 9/16″ diameter 20 TPI thread. The threads are also reversed on the left side pedal to prevent the pedal from loosening under use. Another set of standards is commonly used in the connection from the bottom bracket to the crank. Cranks are connected to the bottom bracket using one of several known standards. Typically, the crank/bottom bracket connection uses a cottered connection, a square taper, or a splined connection. The existing interfaces are difficult and expensive to machine, and they also do not evenly distribute the load be transferred. In the case of the bottom bracket/crank connection, the loads are typically line loads concentrated at the edges of the cotter pin, square taper, or splines. In the case of the pedal/crank connection, the threads often come loose or are damaged during installation (e.g. due to cross-threading).
The standards previously in use for connecting the components of the drive train have worked reasonably well historically, but recent changes have rendered their use problematic. First, riders have become heavier and/or stronger. Riders are consequently capable of applying more load to the components of the drive train, and this increased load leads to an increased failure rate. Additionally, the advent and increased use of stationary exercise cycles has introduced a new level of requirements for durability in drive train components. Stationary exercise cycles are often used by very strong riders for several hours each day. The increases in loads and usage time on the existing components may exceed the loads for which those components are designed.
In addition, reliable and accurate determination of the amount of load exerted on these components has been a difficult question. Users of exercise cycles in particular desire an indication of the amount of load exerted while using the cycles. In the past, attempts to measure loads have relied on mechanical indicators that measure the position of a brake, or complicated, unwieldy electrical sensors. These sensors have proven difficult to calibrate and unreliable.
Another problem frequently encountered on exercise cycles is frame flex. As strong riders exert high load levels on exercise cycles, the frame of the cycle may flex. Frame flex may lead to unpredictable or inconsistent performance of the cycle and may ultimately lead to failure of the frame. Some exercise cycles in the past have approached this problem by having a floor-level connection between the back support of the cycle and the front support of the cycle. This floor-level connection has the disadvantage of occupying additional floor space and reducing the aesthetic appeal of the cycles.
Yet another issue encountered in cycles is chain stretch. Over time, the forces conducted by chains in cycles causes the chain to stretch. As the chain becomes longer, the position of the chain relative to the sprockets may become out of synch. In addition, a loose chain may jump off of one of the sprockets. This type of event puts the cycle out of commission until it is repaired. In typical cycles, the position of one of the sprockets is adjusted periodically to account for chain stretch.
A further issue encountered by users of cycles is the proper positioning and alignment of the saddle. Taller riders typically wish the saddle to be at a relatively high position. Some riders prefer different angles of the saddle relative to the remainder of the cycle. In typical cycles, the height and angle of the saddle are adjustable, but adjustment is a relatively cumbersome process. When the cycle in question belongs to a single person who typically uses the cycle, that person is likely to invest the time necessary to adjust the height and angle of the saddle to a desired position using existing methods. When the cycle in question is an exercise cycle, multiple riders per day may use the cycle; it may be impractical for each user to make height and angle adjustments to the saddle using traditional methods.